Recent studies have demonstrated that the healing response of connective tissue is influenced dramatically by physical forces. A particularly striking functional response has been noted in digital flexor tendons. Studies in our laboratories have shown a variety of favorable responses to early mobilization of digital flexor tendons repaired primarily, including increased strength and excursion, digital angular rotation, peritendinous vascular remodeling, and repair site and sheath DNA content compared to delayed mobilized and immobilized controls. The frequent incidence of poor digital function following one- and two-stage flexor tendon grafts has stimulated a new interest in postoperative protected early motion. Our hypothesis is that autogenous flexor tendon graft healing, not associated with synovial adhesion ingrowth, is stimulated by early controlled motion. In addition, the healing response is donor tissue specific with intrasynovial flexor tendon donors exhibiting greater cellular survival and increased collagen synthesis than extrasynovial extensor tendon donors. We propose that tendon autografts treated by reinstitution of the relevant function of tendon bypass the stages of autograft transformation (avascular necrosis, revascularization, cellular proliferation, and remodeling). Revascularization by adhesions, applicable only to immobilized autogenous grafts, leads to repair that is structurally inferior when compared to grafts mobilized early. The intrinsic healing process, relying on cellular survival and proliferative sheath response when the autograft is immobilized. The objective of this proposal is to determine the specific manner by which flexor tendon autografts heal in the absence of synovial sheath adhesion ingrowth under conditions of early passive motion. The flexor tendon autografts' gliding surface and synovial sheath will be characterized using morphological, biochemical, and biomechanical techniques.